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CLINICAL CHEMISTRY > NPNs > Flashcards

NPNs Flashcards

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1
Q

It is the major NPN in the blood; NPN present in the highest concentration in the blood.

A

Urea

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2
Q

Urea accounts for _____ % of NPNs

A

Urea accounts for 45% of NPNs in the blood.

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3
Q

Urea is the major excretory product of

A

Urea is the major excretory product of protein metabolism.

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4
Q

Urea is synthesized in the

A

It is synthesized in the liver from amino group and free ammonia generated during protein metabolism; it is synthesized in the liver from the deamination of amino acids

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5
Q

Urea is excreted by

A

Urea is excreted by the kidneys

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6
Q

Protein metabolism produces?

A

Protein metabolism produces amino acids which may be oxidized to
(1) produce energy
(2) stored as fat or glycogen

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7
Q

During protein metabolism, nitrogen is

A

During protein metabolism, nitrogen is released and produced as urea in the liver

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8
Q

Following its synthesis to the liver, urea is

A

Following its synthesis to the liver, urea is carried by the blood to the kidneys

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9
Q

In the kidneys, urea is

A

In the kidneys, urea is readily filtered by the glomerulus, where most urea is excreted in urine and some urea is reabsorbed substantially in the PCT (passive diffusion) and inner medullary collecting duct (active transport through urea transporters) during the passage of the filtrate in the renal tubules

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10
Q

Determinants of Urea Conc. in Plasma

A

Thus, the concentration of urea in the plasma is determined by:
1. renal function and perfusion
2. protein content in the diet
3. rate of protein metabolism

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11
Q

Purpose of Urea Measurement

A

Measurement of urea is used to:
(1) evaluate renal function
(2) assess the hydration status
(3) determine the nitrogen balance
(4) aid in the diagnosis of renal disease
(5) verify the adequacy of dialysis

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12
Q

Azotemia is the elevated concentration of

A

Azotemia is the elevated conc. of urea and nitrogenous compounds in the blood

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13
Q

Uremia is the very high or elevated

A

Uremia is the very high or elevated urea plasma concentration accompanied by renal failure. It is eventually fatal if not treated with dialysis and transplantation

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14
Q

Increased plasma urea is classified into

A

Increased plasma urea is classified into 3 main categories according to cause:
(1) Pre-renal azotemia
(2) Renal azotemia
(3) Post renal azotemia

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15
Q

Pre-renal azotemia is caused by

A

Pre-renal azotemia is caused by reduced blood flow; less blood is being delivered to the kidneys thus less urea is being filtered.

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16
Q

Pre-renal azotemia causes

A

congestive heart failure, hemorrhage, shock, dehydration, increased protein catabolism, corticosteroid therapy

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17
Q

Renal azotemia is caused by

A

Renal azotemia is caused by decreased renal function which causes an increase in plasma urea concentration due to compromised urea excretion by the kidneys

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18
Q

Renal azotemia causes

A

acute and chronic renal failure, glomerular nephritis, tubular necrosis

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19
Q

Post renal azotemia is caused by

A

Post renal azotemia is caused by obstruction of urine flow anywhere in the urinary tract (urinary tract obstruction)

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20
Q

Post renal azotemia causes

A

renal calculi, tumors in the prostate and bladder, severe infection

21
Q

Decreased plasma urea concentration causes:

A

low protein intake, overhydration, severe liver disease, late pregnancy and infancy, severe vomiting and diarrhea, malnutrition

22
Q

Specimens used for measurement of urea

A

plasma, serum, and urine

23
Q

Anticoagulants Allowed for Urea Measurement

A

EDTA and Heparin (Sodium Heparin)

24
Q

Anticoagulants NOT Allowed for Urea Measurement

A

Fluoride (Sodium Fluoride) and Citrate (Sodium Citrate) must be avoided

25
Q

Why are fluoride and citrate avoided as anticoagulants in urea measurement?

A

Fluoride and citrate both inhibit urease

26
Q

A fasting sample is (required/not required) for urea measurement.

A

Not required

27
Q

Other specimen considerations for urea measurement

A

Nonhemolyzed samples are recommended; hemolyzed samples are avoided
Urine samples must be analyzed ASAP as urea is susceptible to bacterial decomposition; Urine samples which cannot be analyzed immediately must be refrigerated!
Timed (24-hour) samples must be refrigerated as well.

28
Q

Urinary urea measurements may be used for

A

Urinary urea measurements may be used for the calculation of nitrogen balance

29
Q

Reference Method For Urea Assay

A

Isotope Dilution Mass Spectrophotometry (IDMS)

30
Q

What are the methods of urea analysis?

A

(1) Enzymatic Method of Urea Assay (Indirect Method)
- most frequently used in the clinical laboratory
- (a) Hydrolysis of Urea by Urease , (b) Coupled Urease/ Glutamate dehydrogenase (GLD) Method
(2) Chemical Method of Urea Assay
- (a) Diacetyl Monoxime Method
(3) IDMS

30
Q

What are the methods of urea analysis?

A

(1) Enzymatic Method of Urea Assay (Indirect Method)
- most frequently used in the clinical laboratory
- (a) Hydrolysis of Urea by Urease , (b) Coupled Urease/ Glutamate dehydrogenase (GLD) Method
(2) Chemical Method of Urea Assay
- (a) Diacetyl Monoxime Method
(3) IDMS

31
Q

Urease is aka

A

urea amidohydrolase, E.C. 3.5.1.5.

32
Q

Urease hydrolyzes

A

Hydrolysis of Urea by Urease Principle: Urease hydrolyzes urea in the sample and the ammonium ion which is produced is quantified and may be treated with Berthelot reagents

33
Q

Urease is produced from

A

Jackbeans

34
Q

Creatinine is the end product of

A

Creatinine is the end product of muscle contraction and metabolism derived from creatine (alpha-methyl guanidoacetic acid) and phosphocreatine (a high energy-containing compound)

35
Q

It is excreted in the plasma by the _____ at a rate related to ______

A

Creatinine is excreted in the plasma by the kidneys at a rate related to an individual’s muscle mass.

36
Q

Creatinine measurements in serum and urine are done to

A

Creatinine measurements in serum and urine (creatinine clearance) are done to assess glomerular filtration rate (GFR)

37
Q

Plasma creatinine is _____ to GFR

A

Plasma creatinine is inversely related to GFR

38
Q

Creatinine is an index of

A

Creatinine is an index of overall renal function; it is commonly used to monitor renal function

39
Q

Three Amino Acids that produce creatinine

A

Creatinine is produced by three (3) amino acids:
methionine, arginine, and lysine

40
Q

Creatine is synthesized in the

A

Creatine is synthesized in the liver from AA - methionine, arginine, and lysine

41
Q

Creatine is then transported to the

A

Creatine is then transported to the tissues (muscles) where it is converted to creatine phosphate or phosphocreatine - a high energy-containing compound

42
Q

Creatine phosphate loses ____, whereas, creatine loses ______ and becomes

A

Creatine phosphate loses phosphoric acid, whereas creatine loses water and becomes creatinine- a cyclic compound

43
Q

Creatinine diffuse into

A

Creatinine diffuses into the plasma and becomes excreted by the kidneys into urine

44
Q

Creatinine is not

A

Creatinine is not reused by the body’s metabolism, it is not reabsorbed by the kidneys; thus it is solely a waste product

45
Q

Creatinine is partially secreted by the

A

Creatinine is partially secreted by the proximal tubules via the organic cation pathway

46
Q

Clinical Applications of Creatinine

A

Measurements of creatinine conc. are used to determine:
(1) determine the sufficiency of kidneys/renal function
(2) monitor the progression of kidney disease
(3) determine the severity of kidney disease/damage
(4) measure the completeness of a 24-hour urine collection

47
Q

Plasma creatinine conc. is a function of:

A

(1) function of relative muscle mass- that is, the amount of creatinine generated is directly proportional to muscle mass
(2) function of turnover rate
(3) function of renal function (overall renal function)

CLINICAL CHEMISTRY (3 decks)

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